I look at it the same way House does: everybody lies. People will swear up and down they've done it right, even if they haven't. "Oh, I can't be bothered with that bit, it'll be fine", and so on. Unless I've set up their connection for them, and they're in the same room as me, I can't depend on it.
And of course some people have ISPs that hate gaming traffic, or which randomly change network profiles or shape traffic. Most people don't look into that and only go for what's the "fastest" they can get (without realising why it might be "fast").